A few days passed, and around evening, Ryou and Gyomei arrived at a secluded location deep within the forest. Hidden away, a wooden house stood amidst a sea of wisteria flowers, their blossoms gently swaying in the breeze. Inside the house were Tamayo, Yushiro, and Shinobu.
"Long time no see, Tamayo-san," Ryou greeted with a smile. His gaze then shifted to Shinobu, who looked visibly worn out. "How are you, Shinobu? It seems you've been busy these past few days."
"I'm good, Ryou-san," Shinobu replied. "I'll feel better after some rest, but I couldn't afford to miss this opportunity to defeat Muzan."
Ryou nodded, understanding her. At that moment, Gyomei suddenly asked. "You already know about Tamayo?"
"Yes. I met her during a mission. Since their goal is also to eliminate Muzan, I knew she'd be a valuable ally. I didn't report it to the Demon Slayer Corps because I know how the others will react." Ryou responded.
"I understand!" Gyomei said.
Turning to Tamayo, Ryou asked, "Have you developed the drug?"
"Yes," Tamayo replied softly, "Thanks to Shinobu-san, we developed it. The effect is better than I thought."
She then explained the details of the 'Anti-Kibutsuji Drug'. "It's a unique, potent formula designed specifically to weaken Muzan Kibutsuji. The drug works in stages, but it requires time to take full effect."
Ryou's expression remained calm and asked, "How much time are we talking about?"
Tamayo thought for a moment and said, "First, Muzan must absorb the drug. Once he does, the first stage—Human Conversion—will start. He will attempt to neutralize this stage, but once he does, the next phases will activate."
"So, the first stage acts as a bait?" Ryou asked.
"Yes," Tamayo confirmed. "Even if he doesn't manage to nullify it, the other stages will trigger in order. However, the key to this method is ensuring Muzan absorbs the drug.
But, it won't be easy to get near him and inject this drug into his body. It's nearly impossible."
Gyomei, who had been silent up until now, spoke up. "Ubuyashiki-sama has already made his arrangements. According to him, Muzan will come to him tonight."
Ryou crossed his arms and said. "Indeed. I noticed several demon eyes monitoring my manor yesterday."
"If you can create a distraction, I have a plan to inject the drug into Muzan. With Yushiro's Blood Demon Art, we can make it work," Tamayo said, her eyes sharp with determination.
"Tamayo-sama..." Yushiro murmured softly, his eyes filled with concern as he glanced at her.
Hearing their conversation, Shinobu had a worried look and looked at Ryou. "So, it's happening tonight... Ryou-san, my sister—"
"Don't worry, Shinobu" Ryou said and reassured her. "Kanae is strong. Even if she faces an Upper Moon, she won't be easily defeated. And as for Muzan... leave him to me. He's my responsibility."
---
Midnight arrived, and Muzan Kibutsuji's figure silently walked into the Ubuyashiki mansion. Despite the bandages covering Kagaya's face, leaving only his mouth and nose visible, he could sense Muzan's presence.
"This is our first meeting, right, Kibutsuji Muzan?" Kagaya's voice was calm, showing no fear.
Muzan smiled, eyeing Kagaya. "What a hideous face you have, Ubuyashiki."
"You finally came," Kagaya responded, unbothered by Muzan's insult. He gestured to his wife. "Amane, describe him for me."
Amane described Muzan's appearance. Once she finished, Kagaya spoke again. "I knew you would personally come to kill me."
"I am disappointed, Ubuyashiki. You reek of death... utterly disgraceful." Muzan's expression remained indifferent, but there was a hint of disgust as he took in his enemy's frail appearance.
After that, their conversation played out as it did in the original timeline, with Kagaya calmly speaking and Muzan's irritation growing with every word.
.
.
.
Finally, Muzan had enough. His eyes narrowed, and his fingernails turned into claws. "Have you done talking?"
"To be honest, I never expected you to listen this long. Thank you, Muzan." As Kagaya thanked him, Muzan was further annoyed by the dying man.
At that same moment, the Kasugai crows flew through the night, frantically announcing an emergency summons. Across the region, the Hashira—Sanemi, Obanai, Mitsuri, Muichiro, Kanae, Giyu, Kyojuro, Tengen—and Tanjiro raced toward the Ubuyashiki mansion, horrified that demons had infiltrated their stronghold and they were under attack.
The forest blurred past them as they sprinted, led by their Kasugai crows. If they could just reach the mansion in time, they might be able to save the Ubuyashiki family.
However, just as the mansion came into view, a thunderous explosion occurred, stunning them.
The Ubuyashiki compound was engulfed in flames as a series of hidden explosives detonated, lighting up the night sky like a volcano eruption. The fireball rose high above the trees, triggering a shockwave filled with heat.
Muzan, glaring through the flames, watched with cold expression as Kagaya and Amane embraced death together, their bodies consumed by the inferno of flames.
The explosion tore through the compound, reducing it to rubble. The smell of burning flesh and blood filled the air, a cruel testament to Kagaya's sacrifice.
From a distance, the Hashira froze, horror and disbelief etched on their faces. Tanjiro, sensitive to scents, was overwhelmed by the stench of explosives mixing with the burning scent of flesh and blood.
The sky burned red as the flames climbed higher, and the Hashira were left standing on the edge of the mansion, witnessing the devastating scene unfolding before them.
---
Thrown back by the blast, Muzan winced in agony as his entire body burned showing his bones. Still burning, his body began to regenerate his legs and arms slower than usual.
Through broken skull teeth, Muzan spat, "Ubu... Yashiki..."
'That look on his face...' Muzan recalled Kagaya Ubuyashiki's final moments, 'With a Buddha-like smile he blew himself in an explosion, along with his wife and two children.
I was mistaken. I underestimated him. I thought him to be weak, a frail human no different from the rest. But... he was beyond insane. I was expecting some kind of trap, but not to this extent.'
Muzan's thoughts sharpened as he examined the aftermath of the explosion. 'These explosives were filled with spikes to increase their lethality, designed to delay my regeneration as much as possible. Which means there's more to come...
I sense people gathering here, probably the Hashira. But there's something else. That cunning man used himself as bait.
His rage and hatred toward me coiled deeply in his heart like a serpent. Hiding such murderous intent at such a young age is astonishing.'
Just then, Muzan noticed something unusual around him. Small, red balls of flesh floated in the air, slowly drifting closer to him. His eyes narrowed, "Seeds of flesh? A Blood Demon Art!"
Before he could react, the seeds exploded, bursting into enormous thorns that shot out in every direction. The thorns pierced through Muzan's body, puncturing his head, limbs, and torso. The spikes expanded, branching out inside him, immobilizing him completely.
'I got caught. Whose Blood Demon Art is this?' Muzan's eyes widened in shock as he realized he couldn't move. 'No problem. I just need to absorb them!'
'Shiik!' Suddenly, he felt a sharp pain in his stomach. Muzan glanced down and was stunned to see Tamayo standing before him, her hand piercing through his flesh.
"Tamayo... why are you here?" he snarled in confusion.
'She approached me using a blood demon art of concealment. What is her goal? What has she done?' Muzan thought, noticing talismans tied around her wrists and body.
"So you absorbed my fist, Muzan! What do you think was inside my fist? It's a medicine to turn demons into humans. Can you feel it?" Tamayo asked, feeling her fist absorbed by Muzan.
"No way such medicine exists." Muzan roared.
"I completed it," Tamayo said.
In a sudden surge of anger, Muzan kicked her, sending Tamayo off balance. He followed up swiftly, piercing his thumb into her forehead. "Your grudge is misplaced, Tamayo. You're the one responsible for killing and devouring your husband and children."
At that moment, a flash of movement cut through the mess as Ryou's figure appeared beside Tamayo. With a strong push, he separated Tamayo from Muzan.
Before Muzan could react, Ryou's Nichirin blade sliced cleanly through his neck, severing his head from his body. But he knew this was far from the end.
Activating his Transparent World, Ryou planned to destroy the seven hearts and four remaining brains hidden within Muzan.